PowerShell Get-Item question

Question

I am new to PS. Here is an example of my function codes:

function foo() 
{
    # get a list of files matched pattern and timestamp
    $fs = Get-Item -Path "C:\Temp\*.txt" | Where-Object {$_.lastwritetime -gt "11/01/2009"}
    if ( $fs -ne $null ) # $fs may be empty, check it first
    {
      foreach ($o in $fs)
      {
         # new bak file
         $fBack = "C:\Temp\test\" + $o.Name + ".bak"
         # Exception here Get-Item! See following msg
         # Exception thrown only Get-Item cannot find any files this time.
         # If there is any matched file there, it is OK
         $fs1 = Get-Item -Path $fBack
         ....
       }
     }
  }

The exception message is "The WriteObject and WriteError methods cannot be called after the pipeline has been closed. Please contact Microsoft Support Services."

Basically, I cannot use Get-Item again within the function or loop to get a list of files in a different folder. Not sure why. Any explanation and what is the correct way to fix it?

By the way I am using PS 1.0.

Answer 1

Hi,

I modified the above code slightly to create the backup file, but I am able to use the Get-Item within the loop successfully, with no exceptions being thrown. My code is:

 function foo() 
 {
     # get a list of files matched pattern and timestamp
     $files = Get-Item -Path "C:\Temp\*.*" | Where-Object {$_.lastwritetime -gt "11/01/2009"}
     foreach ($file in $files)
     {
        $fileBackup = [string]::Format("{0}{1}{2}", "C:\Temp\Test\", $file.Name , ".bak") 
        Copy-Item $file.FullName -destination $fileBackup
        # Test that backup file exists 
        if (!(Test-Path $fileBackup))
        {
             Write-Host "$fileBackup does not exist!"
        }
        else
        {
             $fs1 = Get-Item -Path $fileBackup
             ...
        }
     }
 }

I am also using PowerShell 1.0.

Answer 2

This is just a minor variation of what has already been suggested but it uses some techniques that make the code a bit simpler:

function foo() 
{    
    # Get a list of files matched pattern and timestamp    
    $fs = @(Get-Item C:\Temp\*.txt | Where {$_.lastwritetime -gt "11/01/2009"})
    foreach ($o in $fs) {
        # new bak file
        $fBack = "C:\Temp\test\$($o.Name).bak"
        if (!(Test-Path $fBack))
        {
            Copy-Item $fs.Fullname $fBack
        }

        $fs1 = Get-Item -Path $fBack
        ....
    }
}

For more info on the issue with Foreach and scalar null values check out this blog post.